The present invention relates to the field of hydrocarbon upgrading processes. In another aspect, the invention relates to the conversion of cracked gasoline and a lower-alkane diluent in the presence of an improved zeolite material and/or a second diluent to aromatics and ethylene and propylene preferably with an increased conversion of the lower-alkane diluent in the presence of such improved zeolite material and/or the second diluent.
It is known to those skilled in the art that aromatic hydrocarbons and olefins are each a class of very important industrial chemicals which find a variety of uses in petrochemical industry. It can be desirable to co-feed a lower-alkane diluent with gasoline-range hydrocarbons to a process which uses a zeolite conversion catalyst to enhance the conversion of the gasoline-range hydrocarbons. One problem with the co-feeding of lower-alkane diluents is the generally low conversion of the diluent. It is desirable to improve processes for converting gasoline-range hydrocarbons and lower-alkane diluents to aromatics and lower olefins by increasing the conversion of the gasoline-range hydrocarbons and the co-fed lower-alkane diluent.
It is an object of this invention to at least partially convert hydrocarbons, in particular, a hydrocarbon feed mixture comprising cracked gasoline and a lower-alkane diluent, to ethylene, propylene and BTX aromatics.
A further object of this invention is to provide an aromatization process for the conversion of at least a portion of a hydrocarbon feed mixture comprising cracked gasoline and a lower-alkane diluent to aromatics and lower olefins in which the conversion of the lower-alkane diluent is enhanced by co-feeding a second hydrocarbon diluent.
A still further object of this invention is to provide an improved zeolite material that gives improved conversion of a lower-alkane diluent in a process for the conversion of a hydrocarbon feed mixture comprising cracked gasoline and a lower-alkane diluent to aromatics and lower olefins.
Another further object of this invention is to provide a method for making an improved zeolite material having such desirable properties as providing for increased conversion of a lower-alkane diluent in a process for the conversion of a hydrocarbon feed mixture comprising cracked gasoline and a lower-alkane diluent to aromatics and lower olefins.
The invention includes a novel catalyst composition for use in converting hydrocarbons. This novel catalyst composition comprises phosphorus and a calcined, acid-leached zeolite and is prepared by incorporating phosphorus into a calcined, acid-leached zeolite material.
One of the inventive processes provides for the conversion of hydrocarbons to aromatics and lower olefins by contacting under conversion conditions a hydrocarbon feed mixture comprising cracked gasoline and a lower-alkane diluent with a catalyst composition comprising phosphorus and a calcined, acid-leached zeolite.
Another of the inventive processes provides for the conversion of hydrocarbons to aromatics and lower olefins by:
a) introducing a hydrocarbon feed mixture comprising cracked gasoline and a first diluent comprising isopentane to a reaction zone, the reaction zone contains a catalyst comprising a zeolite and a phosphorus component and is operated under reaction conditions for converting hydrocarbons to light olefins;
b) withdrawing from the reaction zone a reactor effluent comprising light olefins; and
c) controllably introducing a second diluent comprising propane into the reaction zone in an amount such that the mole ratio of the second diluent to the first diluent is in the range of from about 1:0.1 to about 1:10, whereby the percent conversion of the first diluent is enhanced over the percent conversion of the first diluent when there is no step c.
Yet another of the inventive processes provides for the conversion of hydrocarbons to aromatics and lower olefins by:
a) introducing a hydrocarbon feed mixture comprising cracked gasoline and a first diluent comprising isopentane to a reaction zone, the reaction zone contains a catalyst comprising a zeolite and a phosphorus component and is operated under reaction conditions for converting hydrocarbons to light olefins;
b) withdrawing from the reaction zone a reactor effluent comprising light olefins; and
c) controllably introducing a second diluent comprising 1-hexene into the reaction zone in an amount such that the mole ratio of the second diluent to the first diluent is in the range of from about 1:0.1 to about 1:10, whereby the percent conversion of the first diluent is enhanced over the percent conversion of the first diluent when there is no step c.
Other objects and advantages of the invention will become apparent from the detailed description and the appended claims.
The inventive composition includes a zeolite starting material that has been treated with an acid followed by calcining to thereby provide a calcined, acid-leached zeolite. The inventive composition further contains a phosphorus component.
An important aspect of the invention is for the starting zeolite material, which is being modified to provide the inventive composition having the desirable properties as earlier described herein, to be treated with an acid to give an acid leached zeolite. A further important aspect of the invention is for the acid-leached zeolite to be calcined to give a calcined, acid-leached zeolite. The calcined, acid-leached zeolite is further modified by the incorporation of a phosphorus component.
Any suitable means or method can be used to treat the zeolite starting material with acid. It is preferred for the zeolite to be soaked with an acid solution by any suitable means known in the art for contacting the zeolite with such acid solution. The acid solution used to treat the zeolite can be a solution of any acid that suitably provides for the leaching of aluminum atoms from the zeolite particles. Preferably, the acid concentration in this solution is about 1-10 equivalents per liter. Examples of such suitable acids include sulfuric, phosphoric, nitric and hydrochloric. The preferred acid solution is aqueous hydrochloric acid solution. The zeolite is soaked in the acid solution (preferably at a temperature of about 50-100xc2x0 C.) for a period upwardly to about 15 hours, but, preferably from 0.1 hour to 12 hours. After soaking, the resultant acid-leached zeolite is washed free of the acid and then can be dried.
The zeolite starting material used in the composition of the invention can be any zeolite which is effective in the conversion of non-aromatic to aromatics when contacted under suitable reaction conditions with non-aromatic hydrocarbons. Preferably, the zeolite has a constraint index (as defined in U.S. Pat. No. 4,097,367, which is incorporated herein by reference) in the range of from about 0.4 to about 12, preferably from about 2 to about 9. Generally, the molar ratio of SiO2 to Al2O3 in the crystalline framework of the zeolite is at least about 5:1 and can range up to infinity. Preferably the molar ratio of SiO2 to Al2O3 in the zeolite framework is about 8:1 to about 200:1, more preferably about 12:1 to about 100:1. Preferred zeolites include ZSM-5, ZSM-8, ZSM-11, ZSM-12, ZSM-35, ZSM-38, and mixtures thereof. Some of these zeolites are also known as xe2x80x9cMFIxe2x80x9d or xe2x80x9cPentasilxe2x80x9d zeolites. The presently more preferred zeolite is ZSM-5.
Any suitable means or method can be used to calcine the acid-leached zeolite. The means or method to calcine generally can include heating the acid-leached zeolite to a temperature in the range of from about 250xc2x0 C. to about 1,000xc2x0 C., preferably about 350xc2x0 C. to about 750xc2x0 C., and most preferably from 400xc2x0 C. to 650xc2x0 C. at a pressure in the range of from below atmospheric upwardly to about 1000 psia (pounds per square inch absolute), preferably from about atmospheric to about 100 psia, and for a time period in the range of from about 0.1 hour to about 30 hours, preferably from about 0.5 hour to about 20 hours, and most preferably from 1 hour to 15 hours.
The inventive composition further includes, in addition to the calcined, acid-leached zeolite, a phosphorus component. The phosphorus component can be incorporated into the calcined, acid-leached zeolite by any suitable means or method known in the art for incorporating a phosphorus component into a substrate material. A preferred method is the use of any standard incipient wetness technique for impregnating the calcined, acid-leached zeolite substrate with a phosphorus component. The preferred method uses a liquid impregnation solution containing the desirable concentration of a phosphorus component so as to ultimately provide the final inventive composition having the required concentration of phosphorus.
The preferred impregnation solution is a solution formed by dissolving a phosphorus compound in a hydrocarbon solvent. The preferred hydrocarbon solvent is hexane. Generally, any phosphorus compounds which can be converted into a phosphorus oxide can be used. Examples of suitable phosphorus compounds include, but are not limited to, phosphorus pentoxide, phosphorus oxychloride, phosphoric acid, organic phosphates, P(OR)3, P(O)(OR)3, P(O)(R)(R)(R), P(R)(R)(R), and combinations of two or more thereof wherein each R can be the same or different and is independently selected from the group consisting of alkyl radicals, alkenyl radicals, aryl radicals, alkaryl radicals, aralkyl radicals, and combinations of any two or more thereof. Examples of suitable organic phosphates include, but are not limited to, trimethylphosphate, triethylphosphate, tripropylphosphate, and combinations of two or more thereof. The presently preferred organic phosphates are trimethylphosphate and triethyl phosphate for they are readily available.
The amount of phosphorus incorporated or impregnated into the calcined, acid-leached zeolite should be such as to give concentrations effective in providing the desirable properties of favorable aromatics and olefin conversion yields with high conversions of a lower-alkane diluent when the inventive composition is employed in the conversion of cracked gasoline and a lower-alkane diluent.
The weight percent of phosphorus present in the impregnated calcined, acid-leached zeolite is generally in the range upwardly to about 10 weight percent of the impregnated calcined, acid-leached zeolite. The preferred concentration of phosphorus in the impregnated calcined, acid-leached zeolite is in the range of from about 1 to about 8 weight percent and, most preferably, from 3 to 6 weight percent.
It is believed that the unique properties of the inventive composition described herein result from the addition of the phosphorus component to the acid-leached zeolite after calcining the acid-leached zeolite. The combination of preparation steps and specific order of such steps gives a composition that provides for an increased conversion of a lower-alkane diluent, comprising a hydrocarbon selected from the group consisting of propane, butane, pentane, and isopentane, in a process for the conversion of a hydrocarbon feed mixture, comprising cracked gasoline and a lower-alkane diluent. The preferred lower-alkane diluent is a hydrocarbon selected from the group consisting of propane and iso-pentane.
The inventive composition described herein can also contain an inorganic binder (also called matrix material) preferably selected from the group consisting of alumina, silica, alumina-silica, aluminum phosphate, clays (such as bentonite), and mixtures thereof. The content of the impregnated calcined, acid-leached zeolite component of the mixture of impregnated calcined, acid-leached zeolite and inorganic binder is in the range of from about 1 to about 99 weight %, preferably from about 5 to about 80 weight %, and most preferably from 10 to 70 weight %, and the content of the above-listed inorganic binders in the mixture of impregnated calcined, acid-leached zeolite and inorganic binder is in the range of from about 1 to about 50 weight %. Generally, the impregnated calcined, acid-leached zeolite and inorganic binder components are compounded and subsequently shaped (such as by pelletizing, extruding or tableting). Generally, the surface area of the compounded composition is about 50 to about 700 m2/g, and its particle size is about 1 to about 10 mm.
Any suitable hydrocarbon feed mixture comprising a cracked gasoline and a lower-alkane diluent, as described above, can be used as the feed to be contacted with the inventive composition under suitable process conditions for obtaining a reaction product comprising lower alkenes containing 2-5 carbon atoms per molecule and aromatic hydrocarbons.
Non-limiting examples of suitable cracked gasoline include gasolines from catalytic oil cracking (e.g., FCC and hydrocracking) processes, pyrolysis gasolines from thermal hydrocarbon (e.g., ethane, propane, and naphtha) cracking processes, naphthas, gas oils, reformates, straight-run gasoline and the like. The preferred cracked gasoline is a gasoline-boiling range cracked gasoline suitable for use as at least a gasoline blend stock generally having a boiling range of from about 30 to about 210xc2x0 C. Generally, the content of paraffins exceeds the combined content of olefins, naphthenes and aromatics (if present).
The hydrocarbon feed mixture can be contacted by any suitable manner with the inventive composition described herein contained within a reaction zone. The contacting step can be operated as a batch process step or, preferably, as a continuous process step. In the latter operation, a solid catalyst bed or a moving catalyst bed or a fluidized catalyst bed can be employed. Any of these operational modes have advantages and disadvantages, and those skilled in the art can select the one most suitable for a particular feed and catalyst.
The contacting step is preferably carried out within a conversion reaction zone, wherein is contained the inventive composition, and under reaction conditions that suitably promote the formation of olefins, preferably light olefins, and aromatics, preferably BTX, from at least a portion of the hydrocarbons of the hydrocarbon feed mixture. The reaction temperature of the contacting step is more particularly in the range of from about 400xc2x0 C. to about 800xc2x0 C., preferably from about 450xc2x0 C. to about 750xc2x0 C. and, most preferably, from 500xc2x0 C. to 700xc2x0 C. The contacting pressure can range from subatmospheric pressure upwardly to about 500 psia, preferably, from about atmospheric to about 450 psia and, most preferably, from 20 psia to 400 psia.
The mole ratio of the lower-alkane diluent to the cracked gasoline should be in the range of from about 1:0.1 to about 1:10, preferably from about 1:0.2 to about 1:8, and most preferably from 1:0.5 to 1:5.
The flow rate at which the hydrocarbon feed mixture is charged to the conversion reaction zone is such as to provide a weight hourly space velocity (xe2x80x9cWHSVxe2x80x9d) in the range of from exceeding 0 hourxe2x88x921 upwardly to about 1000 hourxe2x88x921. The term xe2x80x9cweight hourly space velocityxe2x80x9d, as used herein, shall mean the numerical ratio of the rate at which a hydrocarbon feed is charged to the conversion reaction zone in pounds per hour divided by the pounds of catalyst contained in the conversion reaction zone to which the hydrocarbon is charged. The preferred WHSV of the hydrocarbon feed mixture to the conversion reaction zone or contacting zone can be in the range of from about 0.25 hourxe2x88x921 to about 250 hourxe2x88x921 and, most preferably, from 0.5 hourxe2x88x921 to 100 hourxe2x88x921.
The percent conversion of the lower-alkane diluent in the process for converting the hydrocarbon feed mixture by contacting the hydrocarbon feed mixture with the inventive composition is significantly better than such percent conversion where the composition has not been calcined prior to incorporation of phosphorous therein. Typically, the percent conversion is up to 95% better, but, more typically, the improvement in conversion is in the range of from about 20% to about 90%.
In another embodiment of the invention, it has been discovered that the controlled introduction of a second diluent comprising propane to the reaction zone, along with a hydrocarbon feed mixture comprising cracked gasoline and a first diluent comprising isopentane, for contact with a catalyst comprising a zeolite and a phosphorus component (not necessarily, but preferably, the inventive catalyst described herein) results in increased conversion of the first diluent over the percent conversion of the first diluent in a process where the second diluent is not introduced to the reaction zone.
A percent conversion is identified representing the percent conversion of the first diluent to light olefins and aromatics when there is no introduction of the second diluent. The identified percent conversion of the first diluent when there is no introduction of the second diluent is more particularly in the range upwardly to about 38 weight %. The second diluent is then controllably introduced to the reaction zone resulting in a mole ratio of the second diluent to the first diluent.
The mole ratio of the second diluent to the first diluent can be any ratio that can enhance the percent conversion of the first diluent over the identified percent conversion when there is no introduction of the second diluent. The mole ratio of the second diluent to the first diluent is more particularly in the range of from; about 1:0.1 to about 1:10, preferably in the range of from about 1:0.2 to about 1:8, and most preferably from 1:0.5 to 1:5.
The second diluent can be controllably introduced to the reaction zone in any manner suitable for providing the mole ratio described above resulting in increased percent conversion of the first diluent. The percent conversion of the first diluent when there is a controlled introduction of the second diluent is more particularly in the range of from about 40 to about 90 weight %, preferably in the range of from about 41 to about 80 weight %, and most preferably from 42 to 60 weight %.
The reactor effluent resulting from the practice of this process will have a significant increase in petrochemical concentration (defined as ethylene, propylene, butylenes, benzene, toluene and xylenes) as compared to the petrochemical concentration of the reactor effluent when the second diluent is not introduced to the reaction zone. The reactor effluent may comprise a light olefin, such as, ethylene, propylene, or butylenes, and an aromatic, such as, benzene, toluene or xylenes. It is preferred for the reactor effluent to contain both light olefins and aromatics and, most preferably, the reactor effluent includes ethylene, propylene, butylene and BTX. The weight percent of petrochemicals in the reactor effluent is more particularly in the range of from about 54 to about 90, preferably in the range of from about 55 to about 80, and most preferably from 55 to 70.
The reaction zone is operated at a temperature in the range of from about 400xc2x0 C. to about 800xc2x0 C., preferably from about 450xc2x0 C. to about 750xc2x0 C., and most preferably from 500xc2x0 C. to 700xc2x0 C.; a pressure in the range of from subatmospheric pressure to about 500 psia, preferably from about atmospheric to about 450 psia, and most preferably from 20 psia to 400 psia; and a weight hourly space velocity for the combination of the cracked gasoline, first diluent and second diluent in the range of from exceeding 0 hourxe2x88x921 to about 1000 hourxe2x88x921, preferably from about 0.25 hourxe2x88x921 to about 250 hoursxe2x88x921, and most preferably from 0.5 hourxe2x88x921 to 100 hourxe2x88x921.
The reaction can take place in any reactor system known to those skilled in the art to be suitable for use in converting hydrocarbons to light olefins and aromatics in the presence of a zeolite catalyst. Typical reactor systems useful in the present invention include, but are not limited to, a fixed bed system, a moving bed system, a fluidized bed system and batch type operations.
In a further aspect of this embodiment, the mole ratio of the cracked gasoline to the combination of the first diluent and the second diluent is maintained substantially constant while providing increased first diluent conversion without a substantial change in selectivity of light olefins and BTX formation. The mole ratio of the cracked gasoline to the combination of the first diluent and the second diluent is more particularly in the range of from about 1:1 to about 1:6, preferably in the range of from about 1:2 to about 1:5, and most preferably from 1:3 to 1:4. Maintaining the mole ratio of the cracked gasoline to the combination of the first diluent and the second diluent substantially constant enhances the production of aromatics and light olefins and increases total diluent conversion.
In yet another embodiment of the invention, it has been discovered that the controlled introduction of a second diluent comprising 1-hexene to the reaction zone, along with a hydrocarbon feed mixture comprising cracked gasoline and a first diluent comprising isopentane, for contact with a catalyst comprising a zeolite and a phosphorus component (not necessarily, but preferably, the inventive catalyst described herein) results in increased conversion of the first diluent over the percent conversion of the first diluent in a process where the second diluent is not introduced to the reaction zone.
A percent conversion is identified representing the percent conversion of the first diluent to light olefins and aromatics when there is no introduction of the second diluent. The identified percent conversion of the first diluent when there is no introduction of the second diluent is more particularly in the range upwardly to about 38 weight %. The second diluent is then controllably introduced to the reaction zone resulting in a mole ratio of the second diluent to the first diluent.
The mole ratio of the second diluent to the first diluent can be any ratio that can enhance the percent conversion of the first diluent over the identified percent conversion when there is no introduction of the second diluent. The mole ratio of the second diluent to the first diluent is more particularly in the range of from about 1:0.1 to about 1:10, preferably in the range of from about 1:0.2 to about 1:8, and most preferably from 1:0.5 to 1:5.
The second diluent can be controllably introduced to the reaction zone in any manner suitable for providing the mole ratio described above resulting in increased percent conversion of the first diluent. The percent conversion of the first diluent when there is a controlled introduction of the second diluent is more particularly in the range of from about 39 to about 90 weight %, preferably in the range of from about 40 to about 80 weight %, and most preferably from 41 to 60 weight %.
The reactor effluent resulting from the practice of this process will have an increase in petrochemical (defined as ethylene, propylene, butylenes, benzene, toluene and xylenes) concentration as compared to the petrochemical concentration of the reactor effluent when the second diluent is not introduced to the reaction zone. The reactor effluent may comprise a light olefin, such as, ethylene, propylene, or butylenes, and an aromatic, such as, benzene, toluene or xylenes. It is preferred for the reactor effluent to contain both light olefins and aromatics and, most preferably, the reactor effluent includes ethylene, propylene, butylene and BTX. The weight percent of petrochemicals in the reactor effluent is more particularly in the range of from about 50 to about 90, preferably in the range of from about 51 to about 80, and most preferably from52 to 70.
The reaction zone is operated at a temperature in the range of from about 400xc2x0 C. to about 800xc2x0 C., preferably from about 450xc2x0 C. to about 750xc2x0 C., and most preferably from 500xc2x0 C. to 700xc2x0 C.; a pressure in the range of from subatmospheric pressure to about 500 psia, preferably from about atmospheric to about 450 psia, and most preferably from 20 psia to 400 psia; and a weight hourly space velocity for the combination of the cracked gasoline, first diluent and second diluent in the range of from exceeding 0 hourxe2x88x921 to about 1000 hourxe2x88x921, preferably from about 0.25 hourxe2x88x921 to about 250 hourxe2x88x921, and most preferably from 0.5 hourxe2x88x921 to 100 hourxe2x88x921.
The reaction can take place in any reactor system known to those skilled in the art to be suitable for use in converting hydrocarbons to light olefins and aromatics in the presence of a zeolite catalyst. Typical reactor systems useful in the present invention include, but are not limited to, a fixed bed system, a moving bed system, a fluidized bed system and batch type operations.
In a further aspect of the invention, the mole ratio of the cracked gasoline to the combination of the first diluent and the second diluent is maintained substantially constant while providing increased first diluent conversion without a substantial change in selectivity of light olefins and BTX formation. The mole ratio of the cracked gasoline to the combination of the first diluent and the second diluent is more particularly in the range of from about 1:1 to about 1:6, preferably in the range of from about 1:2 to about 1:5, and most preferably from 1:3 to 1:4.
The following examples are provided to further illustrate this invention and are not to be considered as unduly limiting the scope of this invention.